Simplified system for estimating pulse radar doppler frequency

Abstract

A method for determining doppler frequency by the measurement of the maxi pulse-to-pulse difference over one doppler cycle. A box-carred (sample-and-hold) phase detector's output is differentiated to obtain pulses whose amplitude represents the amplitude of individual boxcar transitions. The largest pulse amplitude is selected for indication of doppler frequency.

Description

Claims

1. In a system having a staircase waveform signal which is amplitude modulated in essentially a sinusoidal manner, the improvement comprises a method of rapidly determining the frequency of the sinusoidal waveform by the steps of: differentiating the staircase waveform signals so as to get a train of pulses whose amplitude corresponds to the waveform; dividing this train into a plurality of channels; utilizing a sample and hold circuit each channel to retain the amplitude of the pulse in that channel; selecting the highest valued pulse in the sampling and hold circuits; and using the pulse amplitude to define the sinusoidal waveform frequency.

2. A method as set forth in claim 1 further comprising the steps of determining the optimum sampling frequency for a given sinusoidal modulation frequency; and dividing the train into separate channels each of which corresponds to a selected dampling frequency.

3. A method as set forth in claim 2 further comprising the steps of providing comparators for each channel; and comparing the highest pulse value with the pulse in each channel and transmitting a signal only when the two are equal.

4. A method as set forth in claim 1 or 3 wherein the system is a MTI radar system; and further comprising the step of determining and selecting the optimum PRI as a function of target doppler frequencies on a real time basis without waiting for the doppler frequency filters to settle.